How to start the National Gas Engine - a step by step guide

The National Gas Engine has one cylinder which currently runs on regular mains gas with spark plug ignition. Starting it is a complex procedure which uses compressed air to turn the engine over, there isn’t a starter motor.
This is the sequence, most of which you can see in the video:
Turn on the cooling water
Release the compression, so that the engine can be turned by hand
Turn the flywheels by hand to get the engine to be just over top dead centre
Engage the governor
Turn on the gas supply
Reset the engine stop switch
Connect the spark plug
Set the ignition to retard for starting
Close the compression valve
Open the compressed air valve in short bursts to turn the engine over. Timing is crucial here, if the valve is open for too long the air will tend to stop the engine.
Once the engine is running advance the ignition for optimum running.